Chlorine dioxide gas is a powerful oxidizer, which is used e.g. in an indoor air environment, for decomposing odorous component for deodorization or for removing/sterilizing virus, bacteria which may be present afloat in the air to cause air-borne infection.
As some examples of conventional methods for determining chlorine dioxide gas concentration in air, there can be cited a method using an electrolysis type sensor utilizing oxidization-reduction reaction and a gas absorption method using iodine solution (see e.g. Non-Patent Document 1).